hurd/hurd/threadvar.h

   1 /* Internal per-thread variables for the Hurd.
   2    Copyright (C) 1994, 95, 97, 98 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #ifndef _HURD_THREADVAR_H
  21 #define _HURD_THREADVAR_H
  22
  23 /* The per-thread variables are found by ANDing this mask
  24    with the value of the stack pointer and then adding this offset.
  25
  26    In the multi-threaded case, cthreads initialization sets
  27    __hurd_threadvar_stack_mask to ~(cthread_stack_size - 1), a mask which
  28    finds the base of the fixed-size cthreads stack; and
  29    __hurd_threadvar_stack_offset to a small offset that skips the data
  30    cthreads itself maintains at the base of each thread's stack.
  31
  32    In the single-threaded case, __hurd_threadvar_stack_mask is zero, so the
  33    stack pointer is ignored; and __hurd_threadvar_stack_offset gives the
  34    address of a small allocated region which contains the variables for the
  35    single thread.  */
  36
  37 extern unsigned long int __hurd_threadvar_stack_mask;
  38 extern unsigned long int __hurd_threadvar_stack_offset;
  39
  40 /* A special case must always be made for the signal thread.  Even when there
  41    is only one user thread and an allocated region can be used for the user
  42    thread's variables, the signal thread needs to have its own location for
  43    per-thread variables.  The variables __hurd_sigthread_stack_base and
  44    __hurd_sigthread_stack_end define the bounds of the stack used by the
  45    signal thread, so that thread can always be specifically identified.  */
  46
  47 extern unsigned long int __hurd_sigthread_stack_base;
  48 extern unsigned long int __hurd_sigthread_stack_end;
  49 extern unsigned long int *__hurd_sigthread_variables;
  50
  51
  52 /* At the location described by the two variables above,
  53    there are __hurd_threadvar_max `unsigned long int's of per-thread data.  */
  54 extern unsigned int __hurd_threadvar_max;
  55
  56 /* These values are the indices for the standard per-thread variables.  */
  57 enum __hurd_threadvar_index
  58   {
  59     _HURD_THREADVAR_MIG_REPLY,  /* Reply port for MiG user stub functions.  */
  60     _HURD_THREADVAR_ERRNO,      /* `errno' value for this thread.  */
  61     _HURD_THREADVAR_SIGSTATE,   /* This thread's `struct hurd_sigstate'.  */
  62     _HURD_THREADVAR_DYNAMIC_USER, /* Dynamically-assigned user variables. */
  63     _HURD_THREADVAR_MALLOC,     /* For use of malloc. */
  64     _HURD_THREADVAR_DL_ERROR,   /* For use of -ldl and dynamic linker. */
  65     _HURD_THREADVAR_MAX         /* Default value for __hurd_threadvar_max.  */
  66   };
  67
  68
  69 #ifndef _EXTERN_INLINE
  70 #define _EXTERN_INLINE extern __inline
  71 #endif
  72
  73 /* Return the location of the value for the per-thread variable with index
  74    INDEX used by the thread whose stack pointer is SP.  */
  75
  76 _EXTERN_INLINE unsigned long int *
  77 __hurd_threadvar_location_from_sp (enum __hurd_threadvar_index __index,
  78                                    void *__sp)
  79 {
  80   unsigned long int __stack = (unsigned long int) __sp;
  81   return &((__stack >= __hurd_sigthread_stack_base &&
  82             __stack < __hurd_sigthread_stack_end)
  83            ? __hurd_sigthread_variables
  84            : (unsigned long int *) ((__stack & __hurd_threadvar_stack_mask) +
  85                                     __hurd_threadvar_stack_offset))[__index];
  86 }
  87
  88 #include <machine-sp.h>         /* Define __thread_stack_pointer.  */
  89
  90 /* Return the location of the current thread's value for the
  91    per-thread variable with index INDEX.  */
  92
  93 extern unsigned long int *
  94 __hurd_threadvar_location (enum __hurd_threadvar_index __index)
  95      /* This declaration tells the compiler that the value is constant
  96         given the same argument.  We assume this won't be called twice from
  97         the same stack frame by different threads.  */
  98      __attribute__ ((__const__));
  99
 100 _EXTERN_INLINE unsigned long int *
 101 __hurd_threadvar_location (enum __hurd_threadvar_index __index)
 102 {
 103   return __hurd_threadvar_location_from_sp (__index,
 104                                             __thread_stack_pointer ());
 105 }
 106
 107 /* Return the current thread's location for `errno'.
 108    The syntax of this function allows redeclarations like `int errno'.  */
 109 _EXTERN_INLINE int *
 110 __hurd_errno_location (void)
 111 {
 112   return (int *) __hurd_threadvar_location (_HURD_THREADVAR_ERRNO);
 113 }
 114
 115
 116 #endif  /* hurd/threadvar.h */